charms of a higher order, I have now arrived at a point where success is no longer doubtful. It must, however, be attained at a very considerable expense, which would not probably be replaced, by the works it might produce, for a long period of time, and which is an undertaking I should feel unwilling to commence, as altogether foreign to my habits and pursuits.'

ARTICLE XIII.

Proceedings of Philosophical Societies.

GEOLOGICAL SOCIETY.

June 21.-Memorandum on a Substance contained in the Interior of certain Chalk Flints, by the Rev. J. J. Conybeare, MGS.

The substance in question is a white powder, giving on a rude analysis, carbonate of lime (slightly tinged by iron), 72; silex (in the state of a fine sand), 28; = 100. The nodule of flint which contained it, presented no apparent trace of any aperture by which it could have entered.

Memorandum on the Comparative Fusibility of certain Rocks, and the Character of the Results, by the Rev. J. J. Conybeare, MGS.

These experiments were undertaken chiefly with a view of comparing the characters of the indurated lias shale (found in contact with the whin dykes) of the north of Ireland with those of certain rocks to which it has been supposed to bear an analogy. The results tend (in the opinion of the writer) to establish the identity of the Irish rock with the shale of the lias formation, as occurring elsewhere, rather than with the true flinty slate or any other variety of basalt. Some experiments of the same nature on other rocks and artificial mixtures of mineral substances are subjoined. They scarcely admit of an abstract.

ARTICLE XIV.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS CONNECTED WITH SCIENCE.

I. Effect of Fixed Oils in destroying the Smell of essential Oils. Mr. Davies, druggist, of Chester, lately pointed out to a friend of 'the Editor, a fact which had accidentally occurred to him, and which he had not seen noticed in chemical books. A mixture of equal parts of castor-oil and peppermint water gradually loses the taste and smell

of peppermint, and in a day or two is entirely deprived of it. The same effect is produced on other distilled waters, and on mixtures of other essential oils with water in the proportion of one drop to two ounce measures of water. When, however, olive oil is substituted for castor oil, a nice palate may distinguish a very slight flavour.

II. Analyses of Magnesite. By M. Berthier.*

This substance, commonly denominated meerschaum, forms with water a viscous and slightly plastic paste, resembling that of starch; it is easily attacked by the strong acids, and it gelatinizes with them: it contains much water of combination, which it gives up entirely at a red heat, without changing its form, or losing its consistence. It consists essentially of silicate of magnesia; but this is almost always mixed with some clay or silicate of alumina.

The analyses were effected in the following manner: The quantity of water was estimated from the loss of weight by calcination; a portion uncalcined was treated with nitric acid, mixed with a little muriatic acid, the solution evaporated to dryness, and treated with acidulated water. The residue was gelatinous silica, mixed, perhaps, with quartz and clay not acted upon by the acids. This, after being calcined, was boiled with liquid potash, which dissolved all the silica; and the undissolved portion was examined by the usual means. The nitric solution was deprived of its alumina and iron by hydrosulphuret of potash, and of its magnesia by potash; the amount of the latter being estimated "par difference."

Magnesite from

Asia Minor.

Cabanas, near
Madrid.

Coulommiers.

Salinelle dep.
du Gard.

Saint-Ouen au pied de Montmartre.

It is evident, says M. Berthier, that these five varieties belong to the same species, and that this species is essentially composed of silica, magnesia, and water; but it is very difficult to obtain a certain knowledge of the relative proportions of these principles, because there are no means of ascertaining the quantity of silica which is found in combination with the alumina.

He concludes, however, after some theoretical reasoning, that the following formula represents the composition of magnesite. 6 M S3 Aq2 + M Aq2-(Annales des Mines, vii. 313.)

III. Analyses of Native Carbonate of Magnesia. By the Same. Carbonate of magnesia is found, either in combination or in mixture,

* The subjects of this notice, in conjunction with those of the following one, constitute the fourth section of a paper by M. Brongniart on the magnesiate of the basin of Paris, &c. an abstract of the preceding sections will appear in our next.

in a great number of limestones; but it also exists in other associations. At Baldissero and at Castella-Monte, it is mixed with silicate of magnesia and with quartz; and in the Isle of Elba, it is mixed with pure silica, which is in a particular state. Four varieties of this carbonate were subjected to an analytical process similar to that described in the foregoing article; the results were as follows:

The quantity of water was obtained by distilling it from the mineral in a retort into a small glass tube; that of carbonic acid by calcination, the weight of the water being subtracted from the loss.

In the mineral of Baldissero, the magnesia which is not combined with carbonic acid, bears the same proportion to the silica as it does in magnesite. In that of Castella-Monte, the proportion of the latter is much greater; and in those of Elba, the magnesia is entirely saturated, leaving the silica free: this silica, however, like that in the calcareous deposits of certain mineral waters, is as readily soluble in alkaline solutions as if it had been obtained in the decomposition of a silicate by an acid.

When the carbonate of Canpo is treated with a strong acid in a boiling state, the magnesia is gradually dissolved with effervescence; but the fragment neither changes its form, nor wholly loses its cohesion; when the solution is poured off, it is found to be semi-transparent like hydrophane, but by desiccation it becomes opaque, and of a very tiful white. It dissolves without residue in boiling liquid potash, and the solution gelatinizes with acids.

beau

"It results from these experiments, that it is not always possible to isolate by means of alkaline solutions, native uncombined silica, from the silica which we separate from a combination by an acid."-(Ibid. p. 315.)

IV. On the Greek Fire of the Middle Ages. By Dr. Mac Culloch.

In No. xxvii. of the Journal of the Royal Institution, is an interesting memoir by Dr. Macculloch, respecting the history and nature of this celebrated subject of inquiry and discussion. The following is a condensed view of the investigation.

The subject of the Greek fire, sufficiently obscure in itself, appears to have been rendered much more so, by collateral causes, and princi

pally by that love of the marvellous in which mankind love to indulge. The historians who have related its effects, and of whom some have even pretended to describe its composition, have involved the subject in perplexities very difficult to disentangle; while succeeding antiquaries and historians, their analysts, have had little better success.

Dr. Mac Culloch apprehends that different inventions, and different kinds of Greek fire, have been described by the same name; that the main source of the confusion can be traced to this cause; and that there is an intimate connexion between the history of the Greek fire, and that of gunpowder.

The common opinion is, that the Greek fire was invented during the reign of Constantine Pogonatus, in the year 668, by Callinicus, an architect of Heliopolis; it was confined, according to Gibbon, for 400 years to the eastern Romans; he adds, that at the end of the eleventh century, the Pisans suffered from it without knowing its composition, and concludes with saying, that it was at length discovered or stolen by the Mahometans; and that in the holy wars of Syria and Egypt, they retorted an invention, contrived against themselves, on the heads of the Christians.

Dr. Mac Culloch observes, respecting this statement, that "the communication between Heliopolis and the eastern nations, renders it, in the first place, suspicious, that the Greek architect borrowed the invention from the orientals. That they possessed it at least before the Greeks, whether they communicated it or not, appears to me as capable of proof as can be expected under similar circumstances. When Gibbon says, that the Mahometans borrowed the invention from the Christians during the wars of the crusades, he forgets that the Arabians learned their chemistry from the Egyptians, by whom that art was practised 300 years at least before the time of Mahomet. That they also borrowed from a still more distant oriental source, appears equally certain."

Naphtha is said to have been one of the chief ingredients in this composition; and that substance is well known to be very common in many parts of the ancient Persian kingdom and in India. Now it is much more probable, that a burning compound in which naphtha was an ingredient, should have been invented where that substance abounded, than where it was unknown; and if it can be proved that the use of inflammable compositions was known to the eastern nations before the time of Callinicus, his claim to this invention falls to the ground. It night, however, have spread among the later Arabians from the Greeks; it became common, and probably from this very source, in the wars of the crusades; "but it is also possible that this, or one of the different inventions known by the same name, might have been discovered by the Arabians themselves, who were then much addicted to chemical pursuits."

One at least of the Greek fires of the crusades was a composition into which nitre entered, and, therefore, depending on the same principle as gunpowder; and thus the two inventions are connected. The art of making fire-works appears to be the original invention, and to have been the true parent of gunpowder, ancient as well as modern. There seems abundant reason to suppose that the cradle of pyrotechny was in the east; in China, the use of fireworks for amusement has

been known from a period beyond all record; and in India, the use of rockets for military purposes is of an antiquity equally obscure.

After some observations on the close analogy which all pyrotechnical compositions bear to gunpowder, Dr. Mac Culloch attempts to trace backwards to the oldest records extant, respecting any preparations of this nature; and these lead us to India, as before observed.

In Grey's Gunnery, printed in London in 1731, is a passage deduced by Philostratus from the life of Apollonius Tyanæus; in this it is said, that Alexander the Great never entered the country of "the truly wise men who dwell between the Hyphasis and the Ganges," "de; terred, not by fear of the inhabitants, but as I suppose, by religious considerations," "for these holy men, beloved by the gods, overthrow their enemies with tempests, and thunderbolts shot from their walls." The Egyptian Hercules and Bacchus are likewise said to have been repulsed from the cities of these people, who were the Oxydrace, by lightning and thunderbolts hurled on them from above. Gunpowder is mentioned in the code of Hindoo laws, which is supposed to reacli back to the time of Moses; and these testimonies are confirmed by a passage in Quintus Curtius, mentioning a compound possessed of similar qualities. Dr. Mac Culloch thinks, however, that the story of the Oxydrace alludes to some kind of rocket.

"If thus far is right, the claims of the early orientals to the Greek fire is established. The Greeks might have received it from the Arabians, or from a more direct source; but it seems likely that Western Europe, at least, is indebted to this people for its knowledge of pyrotechny." It is then shown that this art is of more ancient date among us than is commonly imagined; and having, as above, traced generally the origin of pyrotechny from the east, Dr. M. proceeds to see if some of the particular inflammable compounds, known by the name of the Greek fire, cannot be traced thither also. It is reported by the author of the Esprit des Croissades, to have been known in China in the year 917, and as the Chinese have never been known to borrow arts from the Europeans, and were acquainted with the properly explosive compounds, it is most likely that it was known to them long before. It is said to have been known in China by the name of the oil of the cruel fire. Thus the oily or resinous Greek fire seems to claim an oriental origin as well as the explosive and combustible nitrous compounds.

The Byzantine writers are our earliest European authorities for the names, composition, and effects, of the Greek fire. The Greeks called it the liquid, or maritime fire, probably from its application in naval engagements; "Procopius, in his history of the Goths, uses the same term as the Chinese, calling it an oil, Media's oil, as if it had been some infernal composition of that noted sorceress. But the historian seems to have borrowed this term from Pliny, who calls naphtha a Muda, a sort of proof, by the way, that naphtha entered its composition. :> * Cinnamus also calls it up Mnduxer; and all these names

There is a little confusion in this passage of Dr. Mac Culloch's valuable memoir, which appears to have arisen in part from a somewhat obscure note in Gibbon's History, quarto edition, vol. v. p. 402. ~ Procopius, in his account of the celebrated siege of Petra, describes the use of what must have been a variety of the Greek fire, and says that it consisted of sulphur, and of bitumen which the Medes called naphtha, and the